The long-term goal of this program is to advance our knowledge of ligand-cell surface interactions and apply it to the design, synthesis and implementation of new cellular delivery agents. Towards this end, we have synthesized a series of guanidinoglycoside transporters by derivatizing aminoglycosides and have shown that various cell lines bind and take up the compounds efficiently via negatively-charged cell-surface proteoglycans containing the glycan, heparan sulfate. The guanidinoglycosides act as transporters, enhancing the cellular uptake of otherwise impermeable molecules. The specific aims provide a comprehensive approach for the design and synthesis of new guanidinoglycosides, assessment of their cellular uptake and localization in different cell lines, and their evaluation of their ability to deliver cargos of therapeutic potential: AIM 1. Synthesize systematically modified guanidinoglycosides and evaluate their cellular uptake. To understand comprehensively the impact of the overall charge, as well as the distribution and three- dimensional projection of guanidinium groups, a series of derivatives will be synthesized. A structure-activity-relationship will be developed using cell-based assays for binding and uptake with the objective of identifying the most effective delivery vehicle. AIM 2. Evaluate binding and uptake of guanidinoglycosides in different cell types. The binding and uptake of guanidinoglycosides in human and murine tumor cells and in human fibroblasts will be investigated and compared to the mechanisms in CHO cells. AIM 3. Synthesize and evaluate cellular uptake of guanidinoglycoside-drug conjugates. The most promising guanidinium-containing derivatives will be conjugated to molecular cargos (including small molecules and high MW proteins) and their cellular uptake will be evaluated. We will examine if delivery of toxins can be exploited to block tumor growth and if lysosomal storage deficiency can be corrected by enzyme replacement mediated via transporters. A mechanism-based development of transduction scaffolds will identify lead structures and facilitate the development of useful drug delivery vehicles. New molecular delivery vehicles will expand the repertoire of tools available to control the localization and release of therapeutics. The proposed work thus aims to acquire information about new transporters and provide a platform for treating disease.